PURPOSE: The purpose of this study is to determine whether human gastric adenocarcinoma expresses Fas-L, whether serum sFas-L level is changed in patients before and after gastrectomy, and whether Fas-L or sFas-L is concerned in tumor stage and histologic type. MATERIALS AND METHODS: The authors analysed 38 cases of early gastric carcinoma (EGC) and 61 cases of advanced gastric carcinoma (AGC) who received gastric resection from 1997 to 1998, in whom the number of diffuse type is 38 cases and the number of intestinal type is 61 cases. The authors used immunohistochemical staining for tumoral Fas-L detection and sFas ligand ELISA kit for serum sFas-L detection. RESULTS: Fas-L was localized to neoplastic cells in 61% (23/38) cases of EGC group and 66% (40/61) cases of AGC group. The extent of Fas-L expression was variable, with both FasL- positive and -negative neoplastic region occuring within tumors. The mean serum sFas-L level was highly significantly higher in patients before treatment compared with controls, whereas in patients in post-gastrectomy was significantly lower as the level of controls. Some patients whose preoperative serum sFas-L levels were within normal limits expressed no tumoral Fas-L. In addition, factors such as tumor stage, histologic subtype and other prognostic factors were not concerned in Fas-L expression and serum sFas-L level. CONCLUSION: The authors demonstrate a statistically significant expression of tumoral Fas-L with concomitant increment of serum sFas-L in gastric adenocarcinoma. This finding suggests Fas-mediated apoptosis in response to Fas-L expression by gastric adenocarcinoma, and provide the evidence to support the Fas counterattack and indicate that the serum sFas-L level is a useful indicator in evaluating preoperative diagnosis and postoperative follow-up of gastric adeno- carcinoma. In addition, every clinical stages of gastric adenocarcinoma of the intestinal and the diffuse type not differ in their expression of the Fas and sFas-L.